The present invention relates to a surface mount device such as a resistor or diode, and to an electrical connector having such a surface mount device.
As is known, a surface mount device (SMD) is an electrical device particularly useful in manufacturing circuit boards and the like. Such SMD may be a two-terminal device such as a resistor, a capacitor, an inductor, or a diode; a three-terminal device such as a transistor, a four-terminal device; etc.
In one preferred form of SMD, electrical leads do not extend therefrom. Instead, the SMD includes electrodes integral with the surface thereof. That is, such electrodes are positioned on a contact surface of the SMD such that the electrodes contact corresponding conductive pads on a substrate when the contact surface is brought into aligned contact with such substrate. Typically, a solder or the like is employed to securely bond the SMD to the substrate by way of the electrodes at the contact surface and the corresponding conductive pads and in doing so to maintain a good electrical connection between such electrodes and conductive pads.
As should be understood, then, the lack of electrical leads allows the aforementioned SMD to be relatively small as compared with a conventional circuit element having leads. Accordingly, the real estate used by such SMD on the underlying substrate (i.e., the circuit board) is also relatively small, with the net result being that more circuitry may be placed on the substrate in a smaller space if SMDs are employed as circuit elements.
In one typical two-terminal SMD 10, such as that shown in FIG. 1, the actual circuit device (i.e., a resistor, a capacitor, an inductor, a diode such as an LED, etc.) is encased within a generally rectilinear block 12, and each electrode 14 extends from a top side 12t to an end side 12e and then to a bottom side 12b of the block 12. As maybe appreciated, the portions of the electrodes 14 at the bottom side 12b of the block 12 define a contact surface 16 that faces and at least partially contacts a substrate 18, and such electrodes 14 at the contact surface 16 are positioned to align with corresponding conductive pads 20 on the substrate 18.
A protrusion 22 may extend from the top side 12t of the block 12 between the electrodes 14. Such protrusion 22 may for example contain the operative portion of an LED if in fact the SMD 10 is an LED. In addition, a mounting pad 24 may be present at the bottom side 12b of the block 12 between the electrodes 14. Such mounting pad 24 forms a portion of the contact surface 16 along with the portions of the electrodes 14 at the bottom side 12b of the block 12, and may assist in securely bonding the SMD 10 to the substrate 18.
The SMD 10 as shown in FIG. 1 is entirely appropriate for being mounted to the substrate 18 as shown, where the electrodes 14 at the contact surface 16 align with the corresponding conductive pads 20 on the substrate 18. However, the SMD 10 may not be appropriate for being mounted to other substrates. For example, it may be desirable to mount a SMD 10 containing an LED to a conductive substrate such as a shield of an electrical device, where the LED SMD 10 is coupled to the electrical device and is present on the conductive shield of such electrical device as a visual indicator of some function of the electrical device. However, mounting such LED SMD 10 to such shield by way of the contact surface 16 of such LED SMD 10 would of course produce the unwanted effect of shorting out the LED SMD 10.
Accordingly, a need exists for an SMD 10 that could be employed in a situation where the SMD 10 is not being mounted to a substrate 18 having conductive pads 20 that correspond to the electrodes 14 on the contact surface 16 of such SMD 10, and also in other similar situations.
In the present invention, the aforementioned need is satisfied by a surface mount device (SMD) having a plurality of electrodes and a generally planar contact surface for facing and at least partially contacting a substrate such as a conductive shield. At least one electrode is present at the contact surface and electrically contacts the substrate. In several embodiments of the present invention, at least one electrode is absent from the contact surface and does not electrically contact the substrate. In these embodiments of the present invention, the shield is part of an electrical device which has a lead electrically coupled to the at least one electrode absent from the contact surface. In another embodiment, the SMD includes all electrodes and is mounted to a split conductive shield.